The present invention relates to an apparatus for controlling the turn of a ship which is used to steer a working ship having a plurality of propelling equipment such as an anchor handling tag supply vessel and, more particularly, to an apparatus for controlling the turn of a ship in which the ship can be turned around a stern as a rotational center with the position of the hull held.
Hitherto, in working ships which are used in material handling to the oil digging rig which is known as an anchor handling tag supply vessel, for example, as shown in FIG. 1, two rudders 2L and 2R, two variable pitch propellers 4L and 4R, and a bow thrustor 6 to obtain the thrust in the leftward or rightward direction of the bow are equipped, and these five thrust equipment are individually controlled by independent levers.
The works which are required for such working ships include: the supply of material to the rig in the state which is close to the oil digging rig; the loading and unloading of material by the crane of the rig; the anchor handling for moving and mooring the rig; and the like. In these works, it is required to delicately steer the ship at a slow speed in the disturbance such as wind, tidal current, and the like. Practically speaking, the ship steering operations in this case include the turn, lateral movement, inclined sailing, holding of the specific point at sea, holding of the bow azimuth, and the like at the same position.
For those severe requirements, the ship operator must continue the works for a long time while adjusting the respective control levers in accordance with the situation in consideration of the performances of the five thrust equipment of the ship. Thus, even the skilled ship operator is accompanied with the fairly large mental and physical burden.
Therefore, to reduce the burden for the ship operator, for example, with respect to the control of the turn of ship, the apparatus constituting the closed loop as shown in FIG. 2 has been considered. Namely, an azimuth setting knob 10 is provided. The deviation .psi..sub.e between a set azimuth .psi..sub.i of the knob 10 and the bow azimuth .psi. of a hull 18 which is detected by a gyro compass 20 is obtained at an adding point 12. A pitch angle P.sub.0 of the bow thrustor 16 is varied by a PID control unit 14 so as to completely eliminate the azimuth deviation .psi..sub.e, thereby controlling the thrust T.sub.b.
However, in such a conventional turn control apparatus, another azimuth setting knob is needed to control the turn of ship in addition to the operating levers to move the ship forwardly, backwardly, obliquely, and the like. On the other hand, this apparatus intends to merely turn the ship by the bow thrustor so that the bow is simply directed to the set azimuth. Therefore, it is impossible to perform the peculiar turn control such as to turn the ship near the oil digging rig without changing the position of the ship, which control is required in working ships such as anchor handling tag supply vessels. Further, there is also the problem such that the turning velocity cannot be freely changed.